4x4 Help

[casper98]

Today while in the mountains i was putting the vehicle in 4low. The truck would start out okay but when going up a trail you could feel the truck kind of cut out then surge. It did this four about two minutes until i got to a spot where i could put it in 4high. The problem does not happen in 4high at all, only in 4low. What could be causing this problem?

[jro909]

how fast were you going? 4lo is for shit on a shingle speed...go any faster it will dog or bind...

[casper98]

Maybe 5-10mph, I was going up a dirt trail so really there was hardly any speed.

[RyanbabZ71]

I could be wrong but dont you have to be stopped to engage 4 Lo?

[casper98]

You do have to be stopped to engage 4low. I didn't engage it when i was driving, I engaged it before I went up the trail.

[mtiffinal]

Could the surge have been a gear shift? If I use low, I'll pull the tranny down to first to prevent the hard shifts.

 

One more thing, did you notice what the RPM's were doing?

[peterarch]

4WD low will surge at 5-10 mph because of the great increase in torque when you switch into those gears. Its only meant for extreme offroad maneuvers at extremely low speeds or pulling extremely heavy loads at very low speeds. It gives the engine much more torque and pulling power as well as locking the differential. So yes, if you even tap the gas when your around 2000rpm in 4wd lo it will definitely surge

[casper98]

It just seemed a little weird that it does it in 4lo and not 4high. I have a 99 5.3, do both the front and rear differentials lock in 4lo?

[peterarch]

4wd high uses the same gearing system as when your in 2wd. All your doing is engaging the front wheels. With 4wd low you engage a whole different gearing system that allows you to gain the maximum horsepower and torque out of your engine at extremely low speeds, to either help your vehicle climb extremely difficult obstacles or pull extremely heavy items with the maximum that your engine can put out. To do this is lowers the gear ratios significantly so the engine may be running at 4500 rpms but your only going like 5mph, at that rpm if you tap the gas and let go the truck will feel like its surging because of the extremely increased amount of torque from that gearing ratio at those rpms. as corrected below the diffs are not locked in 4wd low. my misunderstanding

 

A perfect example of this is today i used 4wd low to pull a ford off a beach after it made ruts and got stuck hahaha

 

The key to all of this is extremely low speeds, you should not be going over 5mph i would say while performing any maneuvers in 4wd low or it could be very damaging

[casper98]

Thanks for the input guys, I just wanted to make sure nothing was wrong with the truck.

[hockeypro1411]

4WD low will surge at 5-10 mph because of the great increase in torque when you switch into those gears. Its only meant for extreme offroad maneuvers at extremely low speeds or pulling extremely heavy loads at very low speeds. It gives the engine much more torque and pulling power as well as locking the differential. So yes, if you even tap the gas when your around 2000rpm in 4wd lo it will definitely surge

 

False.

[peterarch]

ok that was the one thing i wasn't positive about, but the rest i know

[hockeypro1411]

Everything else is correct.

[casper98]

So it doesn't lock the differential?

[hockeypro1411]

So it doesn't lock the differential?

 

No. 4lo does nothing with the differential. If you have the G80 locking diff., it's a fully mechanical locker. There's no way to lock it except to spin one tire ~100 RPM faster than the other.